Method of and apparatus for the protection of copper



March 5, 1957 A. MAURIN 2,784,156

METHOD OF AND APPARATUS FOR THE PROTECTION COPPER Filed June 29, 1954 METHOD OF AND APPARATUS FOR THE PROTECTION OF COPPER Alexandre Maurin, Paris, France, assignor to Compagnie de Construction de Gros Materiel Electro Mecanique, Paris, France, a company of France Application June 29,1954, Serial No. 440,191 Claims priority, application France August 3, 1953 8 Claims. (Cl. 204-147) Condenser tubes supplied with sea water, for example those which are installed on board ships and those installed in power stations on land in the vicinity of the sea, are usually made of copper or copper alloys (brass with or without arsenic, to which tin is added, if necessary, and cupro-nickels to which may be added iron and manganese) In spite of the great resistance of copper and its alloys to corrosion by sea water, such corrosion is not negligible in certain cases, and in particular when the water contains an appreciable quantity of organic matter and micro-organisms.

It is an object of the present invention to provide an improved method for preventing corrosion of copper and alloys of copper in contact with saltwater, especially in the case of condenser tubes through which sea water is circulated.

'Duringthe course of my researcheson corrosion in such conditions, I have found that, in order to achieve the desired result, it is desirable to form a' homogeneous protecting layer of iron oxide FezOs on the surfaces of the copper or the copper alloys, and to maintain this layer on these surfaces by attacking the causes of deterioration of such a layer; furthermore, Ihave found that there is no corrosion at all when the surface in question is directly covered with the oxide FezOa; that the corrosion is small when there is present an intermediary layer of oxide CuzO, and that, on the other hand, the corrosion is considerable when the surface is coated with cuprous chloride CllCla which is itself covered with a coating of iron oxide F8304; there is produced by reduction through the agency of bacteria,

the hydrogen sulphide being produced by sulfate-reducing bacteria (e. g. Sporovibrio desulfuricans) as explained for example in Herbert Uhlig, Corrosion Handbook, page 469, November 1953, John Wiley & Sons, publishers.

The invention includes the process in accordance with which the salt water, which is destined to come into contact with the surface to be protected, is permanently subjected to an electrolytic action by means of an iron anode, so as to give rise to the formation and transportation of chlorine which plays the part of an oxidising agent and of a bacteria-killing substance, and also ferrate ion FeOr which for example is able to be converted to FezOs by reduction.

There is an advantage in completing this process by a treatment which enables the formation of a coating of copper oxide, which is insoluble and serves to protect the surface of the copper or copper alloy, the coating being preferably in the form of a brown complex of manganese dioxide MnOz and copper oxide CuO.

To this end, it is recommended to treat the surface in the first place with an aqueous solution of a permanganate, in particular potassium permanganate, for example a solution containing about 0.2 to 0.4 gram of this salt per litre of fresh water. If necessary, the surfaceto be protected may be-first of all cleaned, de-greased and pickled following any oneof the known techniques.

In addition, with the object of maintaining the deposit of manganese dioxide on the surface to be protected, it is an advantage to employ a manganese anode, in addition to the iron anode, for the electrolysisof the water which comes into contact with the surface in question;- in this way there'is formed a manganese ion MnOr which can be reduced to manganese dioxide;

The reduction of the oxides is mainly effected by the cathode means of hydrogen which is given off at together with sodium hydroxide. 7

In the case in which the surface of copper or copper alloy is representedby condenser tubes supported by tubular plates which-arethemselves mounted in a casing made of a ferrous alloy, this casing will preferably be employed as the cathode,'since it is then along thewalls thereof that sodium hydroxide is produced in the nascent state and makes the water alkaline,'by virtue of whichthe said walls are protected against corrosion. In addition, the concentration of copper chloride on the walls of the tubes is thereby reduced, since such concentration becomes progressively less as the degree of alkalinity of the water increases. H I

' Finally, the invention comprises a protective arrange' "ment whichwill beillustrated by means of an example of its application to a tubular condenser. I

The description which follows below with respect to the attached drawing (which is given by way of example only andnot in any sense byway of limitation) will make it quite clear how the invention may be carried into effect, the special features which are brought out, either in the text or in the drawing, being understood to form a part of the said invention.

The single figure'represents a diagrammatic illustra tion of a tubular condenser employing circulation of salt arrangement for protecting,

water and provided with an it against corrosion.

The condenser comprises a bundle of tubes 1, of copv per or copper alloy, held in tubular plates 2, 3. The latter are enclosed in' a casing, the 'end members 4, 5, of: which are, for example, made of cast-iron and'the cy-' lindrical wall 6, of sheet steel.

Inaccordance with a special feature of the invention, the tubular plates 2, 3 instead of being directly fixed to the wall 6, arefixed to it through the medium of in-.

sulating joints 7, 8, which prevent any'direct electrical" contact between the copper and the iron.

The casing 4, 5, is supplied with salt water for cooling (for example sea water) through a pipe 9, for example by means of a pump 10, and this water egresses through a pipe 11; the pump 10 draws water from an incoming feed channel 12.

In accordance with the present invention, an iron anode which may be composed of a number of plates 13, is immersed in the channel 12 whilst a second anode 14 made of manganese is preferably located inside the inlet chamber 15 for easing 4, 5. The end members 4, 5 are employed as cathodes, the various electrodes 13, 14, 4, 5,

being connected, for example, to a rectifier which has been shown diagrammatically at 16.

The electrolytic protection arrangement which is thus added to the condenser and to its water supply system ensures the formation of ferrate ion FeOr along plates 13, this oxide being then conveyed by the water circulated by the pump; it also ensures the production at the anodes Patented Mar. 5, 1957 point .of -its entry into, the ,casing 4,, ,5, which thereby zone-having a cathode and anironanodetherein so as to form an alkaline cathodic product and aniron-containinganodic product in said water in said zone, and continuously passing the whole effiuent from said electro ly zing zoneincluding said cathodic and anodic products along said surface.

2.- A process for preventing corrosion by salt water, of the surface of a material containing copper which in operation is in contact with flowing salt water, which comprisesthe initial step of oxidizing said surface to provide aprotective film containing copperoxide CuO thereon; then the step of continuously passing said flowing salt water before it reaches said surface, through an electrolyzing zone having a cathode and an iron anode therein so as to form an alkaline cathodic product and an ironcontaining anodic product in said water in said zone, and continuously passing the whole effiuent from said electrolyzing zone including said cathodic and anodic products along said, surface.

3. A process for preventing corrosion. by salt water, of the surface of a material containing copper which in operation is in contact with flowing salt water, which comprises the initial step of contacting an aqueous solution of an alkali metal permanganate with said surface tooxidize the same superficially and to provide a'protectivefilm of a brown manganese dioxide-copper oxide complex salt thereon, then the step of continuously passing said flowing salt water before it reaches said surface, throughan electrolyzing zone having acathode, an iron anode and a manganese anode between said iron anode and said surface, so as to form an alkalinecathodic productandan irons and manganese-containing. anodic. prod- 1 net in said zone, and passing the whole effluent from said electrolyzing zoneincluding said cathodic and anodic products along said surface.

4. In aheat exchange plant comprising ,a;heat. errchangeisurfacemade of a material containing copper, the

combinationofasalt waterreceiver, spaced apart from said heat exchange surface; a source of direct electric current; an iron anode in said receiver connected to said source, for producing an anodic product in the salt water in said receiver; piping means .for leading said salt water with said anodic product therein from said receiver to said heat exchangesurface and passing the same. along said surface; and acathode in said piping means at a point intermediate said iron anode and said heat exchange surface, connected to said source for producing a cathodic product in said salt water containing said anodicproduct on its way to said heat exchange surface.

5. The' combination of claim-4, further comprising a manganese anode, connected to said source, at apoint intermediate said iron anode and said heat exchange surface.

6. In a heat exchange plant, the combination of a condenser including a bundle of tubes made-of-,a;ma terial containing copper; means comprising aninlet heading. secured to but electrically insulated from said bundle of tubeson the inlet side thereof, for leading salt water to I the inlet end of said tubes and through said tubes; aniron anode in said means at a point upstream with respect. to said inlet heading; a cathode in said inlet heading; and; asource of direct electric current between-said anode and a said cathode.

7. The combination of claim 6, further comprising; a manganese anode in'said heading.

8: In a ;heat exchange plant, the combination of a condenser including a bundle of tubes made of a material containing copper; an iron inlet heading and an iron outlet heading for said condenser, securedto but electrically insulated from said condenser; means for feeding salt.{ water to said inlet heading and passing the same through said jtubes'into and out of said outlet heading; an iron anode in said rneans at a point upstream with respect to said inle't heading; a manganese anode withinsaid inlet, heading, supported and electrically insulated therefrom; a. source of-direct'electric current; meansfor electrically connecting said iron headings to the negative terminal of; said source; and means for electrically connecting said iron anode and manganese anode to the positive terminal of said source.

References'Cited in the file of thispatent UNITED STATES PATENTS- 

1. A PROCESS FOR PREVENTING CORROSION BY SALT WATER, OF THE SURFACE OF A MATERIAL CONTAINING COPPER WHICH IN OPERATION IS IN CONTACT WITH FLOWING SALT WATER, WHICH COMPRISES CONTINUOUSLY PASSING SAID FLOWING SALT WATER BEFORE IT REACHES SAID SURFACE, THROUGH AN ELECTROLYZING ZONE HAVING A CATHODE AND AN IRON ANODE THEREIN SO AS TO FORM AN ALKALINE CATHODIC PRODUCT SAND AN IRON-CONTAINING ANODIC PRODUCT IN SAID WATER IN SAID ZONE, AND CONTINUOUSLY PASSING THE WHOLE EFFLUENT FROM SAID ELECTROLYZING ZONE INCLUDING SAID CATHODIC AND ANODIC PRODUCTS ALONG SAID SURFACE. 